The invention relates to a novel candle formulation that burns with a colored flame free of the yellow color associated with the familiar paraffin candle.
One of the requirements for a candle burning with a true, one-colored flame is removal of the yellow color, found in the common paraffin candle, for example. Briefly, the burning process is thought to involve the following steps: (1) melting of the solid wax by the heat of the flame; (2) migration of the liquid wax toward the flame zone through the wick; (3) vaporization of the liquid wax; (4) incandescence of the wax vapor as it rises into the flame; (5) combustion of the wax vapor to carbon dioxide and water as it mixes with the oxygen of the air that diffuses into the flame. In a gas stove, on the other hand, the fuel, already in the gaseous state, can be pre-mixed with the air required for combustion, and the familiar pale-blue flame thus arises from fragments of molecules that appear and disappear continuously during the combustion of the gas. In fact, the pale blue color can be observed even in the familiar candle flame, in those areas where air can most easily reach, i.e., the outside surface of the bottom part of the flame. In other areas of the flame, the pale blue color is present, but is obscured by the yellow. Therefore, a candle which eliminates the yellow color, leaving only the pale blue, gives a flame of one pure color and constitutes a substantial improvement.
Since the presence of air, or more accurately, oxygen, in the flame zone is the key to elimination of the yellow color, previous attempts have employed four methods: (1) use of a wax or fuel which is made up of molecules containing sufficient numbers of oxygen atoms, e.g., polyethylene glycols; (2) introduction of an additive containing a high proportion of oxygen atoms as an oxidizing agent, such as ethylene carbamate; (3) dispersion of air in the solidifying wax; (4) use of the flame colorant as the fuel as well. All of these attempts have suffered serious disadvantages.
One method uses a fuel that incorporates suitable amounts and distributions of oxygen atoms. German patent 1,226,234, uses polyethylene glycols, polymers with repeating units of three atoms, two carbon and one oxygen, in the polymer chain. Polyethylene glycols of the molecular weight specified in the patent are waxy substances, similar in appearance to paraffin, and require a wick to transport them to the flame, following the combustion mechanism described above. Moreover, according to the patent, the oxygen already present in the fuel (about 36.4% by weight) requires augmentation in order to maintain combustion. The three additives, ethylene glycol, glycerin, and ethyl carbamate, specified in the examples, are added in amounts sufficient to raise the oxygen level to between 38.7% and 39.8%. The patent also recognizes that the molten fuel is more viscous than molten paraffin, and thus flows more slowly up the wick, and recommends the use of an appropriate wick of denser cross section and lesser thickness. However, a denser wick collects more difficultly combustible products, introducing the familiar yellow color into the flame. Indeed, the problems associated with the wicks of ordinary candles have been addressed in subsequent disclosures, either by additives to the wick, or by eliminating it. The above cited patent, therefore, leaves one with the choice of a small flame of pure hue, or a larger flame with a yellow core.
An attempt to improve on the candle of the patent cited above is disclosed in German patent 1,945,120, which reverts to paraffin as the fuel, but emulsifies the fuel with air. However, this candle is difficult to produce. The example provided requires, first, preparation of a flame-coloring agent with three components, the concentrations and cooling of which must be carefully controlled; second, a wick which must be coated with paraffin by repeated dipping; third, application of the flame-coloring agent to the coated wick in a layer applied as strips, the edges of which must not touch, and the total amount of which must be carefully controlled; fourth, an air-paraffin emulsion prepared by inspirating paraffin which must be held precisely at a temperature just under the solidification point (presumably even under the cooling influence of the gas); and finally, immediate transfer of the emulsion into a mold containing the components of the candle already described.
Another proposal, disclosed in German patent 2,364,506, uses a fuel of metaldehyde, a polymer with a repeating unit of two atoms, carbon and oxygen, in the polymer chain and with an additional carbon atom attached to each of the carbon atoms in the main chain. Since the polymer is so much more combustible than polyethylene glycol, it supports a flame directly, without requiring a wick. Consequently, a coating is necessary to control combustion and prevent the flame from spreading down the side of the candle. The patent discloses the use of a metallic stearate mixed with stearin as the coating, serving also as the flame coloring agent. However, the patent discloses further that the coating by itself is not sufficient to control combustion; in the vicinity of the flame, a metal cup-shaped piece, fashioned to exacting specifications, is required to prevent degradation of the coating itself.
The method of production of the candle is not easy, since the material melts to a liquid only in a sealed tube or container, but sublimes directly to the gas when not enclosed. Moreover, the sealed-tube melting point (246.degree. C., 475.degree. F.) is much higher than the sublimation point (which is reported in various sources as 112.degree. C., 234.degree. F. or 193.degree. C., 380.degree. F., the latter being specified in the patent as the melting point). Therefore, any process used for shaping the metaldehyde core of the candle into the specified core of square cross-section would have to employ a sealed tube at high temperatures.
Finally, disclosure of a candle with a fuel consisting exclusively of a metal stearate alleges to eliminate the problems associated with delivery of the coloring agent up the wick, but does not address the problem of the complete elimination of the familiar yellow color.
In view of the problems listed herein, a candle which burns at an acceptable rate, with a sufficiently large flame from which the normal yellow color has been eliminated, preferably without requiring a wick, without dripping or extensive melting, and leaving a minimal, if any, residue, is highly desirable.